(car engine revving)
- Oh, sounds like a BMW N55.
(car engine revving)
That one sounds like an RB25.
(car engine revving)
Oh, that's a Toyota 2JZ baby.
(car engine revving)
(Eddie speaking off mic)
- Something drive by?
I didn't hear anything.
Now how did I know any of that
without seeing any of those cars?
Well, for one, because I wrote this episode
and those are me and my roommates cars,
but two, because I could hear 'em.
The exhaust note of the car is basically its mating call.
What your car sounds like is a big part of who your car is.
It's like its signature.
Having a cool and recognizable exhaust sound
is one of the main reasons that an aftermarket exhaust
is one of the first upgrades
a lot of people do to their car.
They come in different shapes, sizes, and of course prices,
but they all promise pretty much the same thing,
slightly more horsepower
and a better and generally louder overall sound.
But will they always give you more power?
And if so, how?
And why does one pipe sound different than another?
Today we're gonna install a $600 MagnaFlow
cat back exhaust onto the Miata.
And along the way, I'm gonna answer all of those questions
and more and then we'll take it for a spin
and I'll give you my opinion on whether or not
it was worth it for the old Money Pit Miata.
And hopefully that'll give you enough context
to make the same decision for yourselves.
I'm Zach and this is Money Pit.
Let's do it.
(thunder crashing)
(car engine revving)
Now today's challenge is to make the Miata sound like that.
All right, so we're cruising around
with our stock exhaust right now.
Take a listen.
(car engine revving)
It doesn't really sound like much.
So we wanna put an exhaust on it that's gonna flow
better than stock and sound better than stock.
So let's go back to the garage
and I'll show you what we got.
All right, this is the exhaust that we got,
it's a MagnaFlow.
It costs about $590.
It's made out of stainless steel
so it shouldn't rust or corrode.
Let's get the bubble wrap off and see what we're looking at.
Woo!
Shiny.
So you can see we've got some welds here.
They look nice.
This thing is welded together by robots I believe,
robots tend to not make mistakes.
So that's cool.
So build quality seems pretty good
and really it should for 600 bucks for a cat back,
it's not the cheapest thing in the world.
Let's get the rest of it out.
Oh, what's this?
A little plug for a bum.
So this is our resonator.
These are used to cancel out drone and harsh frequencies.
And you know a rasp.
That's a big muffler.
We got a big honk and resonator and we only have
what is it?
A 1.8 liter, four-cylinder.
I think this should be pretty quiet,
which honestly is what I want.
I don't wanna make that much noise with the Miata.
Yeah,
- [Eddie] Old man,
- It's a 100 horsepower four-cylinder.
We don't need to scream about that.
We can just be quiet.
We can just
(revving)
Like that.
So the way a resonator works,
basically exhaust comes flowing through
and you can see this resonator straight through.
But this outer case is packed full of material.
Sometimes like a fiberglass
or something that absorbs sound and energy.
So as the exhaust goes through,
the packing material absorbs a lot of sound.
It's really simple.
This is a cat backexhaust for a 1994 Miata.
Now when I say cat back, what does that mean?
It means what it says.
The exhaust starts at the end of your stock cat
and goes the rest of the way back.
We're gonna be keeping the stock cat
because again, we're only making a 100 horsepower right now.
So we're okay with the emissions equipment.
It might gain us a horsepower or two.
It should gain us some sound at least.
But, it's gonna take us like 10 minutes to install.
Ten minutes to install.
- [Eddie] Want to make a bet?
- No.
Oops too far.
So, my driveway is slanted downwards
and we're lifting up the rear to put on an exhaust.
That's why I put something in front of the front wheel
so that it couldn't roll away.
Always good to give her a little shake.
Make sure your work is stable.
All right, let's take this old piece of (bleep) off.
All right, so this is our catalytic converter.
So we're going to be replacing everything from here back.
So, I'm gonna start here and pop off these nuts.
But the first thing you should do
is use some penetrating oil,
ideally the night before
or even a few days before you get going.
And, this will kind of seep into those threads
and help break free any of that rust
so that you not end up stripping your hardware
or rounding off any of your nuts.
Okay, so now our nuts are loose.
Now we need to pull the exhaust out of its rubber hanger.
So we're gonna add a little bit of lube
and then we're just gonna force it with some pliers
and screwdrivers and our hands.
Okay, I think we have one more left.
Okay, now
(chuckles)
Is there a ridiculous way to do this?
Now, there's gotta be a way.
Oh, so close.
Think that will be enough?
Eddie thinks so.
- [Eddie] I know so.
- Eddie knows so.
Eddie's the smartest dude ever.
Whoa (bleep)
Okay.
The old exhaust is out.
That was pretty easy.
Even with a couple of little hiccups.
I think it's been 15 minutes.
So removal, installation, this whole thing is not too bad.
So, so far worth it.
Alright, so let's talk about some of the pros and cons
of an aftermarket exhaust to see what all the fuss is about
and see if this thing is actually worth it.
The point of these is to let your engine breathe better.
The exhaling part by increasing the diameter of the piping.
They'll also make the muffler design
a little more free flowing
and they'll remove any unnecessary bends or you know,
sharp turns that you don't need to have.
Just to try to decrease restriction
and improve flow overall in the exhaust system.
Now improved flow and decreased restriction,
can mean you know, a few extra horsepower up top.
They also usually tend to make more noise than stock
due to the decrease in restriction
and the change in muffler design.
Now that part is obviously awesome
as long as the muffler is designed to sound good
and the engine that you're putting it on
is capable of making good noises.
That's a big part of this.
Hit the YouTube and the Google,
find examples of your car with specific exhausts.
Chances are if somebody makes an exhaust for your car,
someone out there has bought it
and someone has made a video of it.
Now, in addition to being louder because we like that,
being louder can also save your life.
You may have heard the phrase loud pipes save lives
and that can be true, especially on a motorcycle
or in a tiny car like the Miata,
making a little noise can make somebody
who didn't see you coming, hear you coming
and not pull out in front of you
or run you over all together.
Okay, so generally aftermarket exhausts
are made out of aluminized steel or stainless steel,
both materials that last a very long time,
which is why a lot of aftermarket exhausts
will come with lifetime warranties like this one
'cause the materials are just good.
Now, okay, let's talk about the cons.
Some cons side of thing.
Let's talk about cons, baby.
Con artists, they can be expensive.
This, just for the Miata was $600.
It's not cheap, it's not nothing.
Generally speaking, the exhaust price
and just aftermarket parts in general are commensurate
with the price of your platform.
So, unexpensive cars,
your exhaust is gonna be a little bit more expensive.
Other than that, you know, there are some people out there
that just don't wanna make more noise.
I know that sounds ridiculous,
but what I'm talking about is drone.
(buzzing)
That's drone.
Automotive manufacturers, OEMs spend a lot of time and money
and brain power making the stock parts
and the truth is the stock parts
are usually really impressive in a lot of ways.
They always tend to land pretty squarely
at the crossroads of comfort, reliability and power,
which is a pretty impressive thing.
Once you replace your exhaust,
you move away from that crossroads of comfort
and reliability and you head down the road to power,
which is a fun road, but it is definitely a lot more noisy.
But how do you know if you need an exhaust?
Honestly, it really depends on the platform.
So you're gonna have to do some research.
Some cars, like big old V8's
or cars that have a really restrictive exhaust
from the factory can gain a lot of power
from just an exhaust where some cars
won't gain much of anything.
And then what kind of exhaust do you need?
A cat back, an axle back, a header back, turbo back?
Literally the AL of those just mean that the exhaust
starts at the end of that thing and goes
all the rest of the way back to the end of the exhaust.
And what you need depends on your goals.
The more of the exhaust system you replaced
with free or flowing parts,
the more power you can potentially make.
So what size exhaust do you need?
Well, the answer is, there's a lot of math
to figure that out, but practically speaking,
there are a lot of calculators and charts online
that will help you determine what diameter pipe to use
for a given horsepower level and engine displacement.
So in that sense, it's pretty simple.
Just look up exhaust diameter calculator
and you'll find everything you need.
Let's put this thing on.
We're just gonna install this pipe first
to the catalytic converter.
I think I should be able to do it this way
and then we'll put the back half on
since the MagnaFlow comes in two pieces.
Now, this brace on its way back up.
Isn't aligning that quite perfect.
So, just giving her the old persuasion,
sometimes we're gonna have a car that sucks.
Like right now. (chuckles)
Before we finish installing this exhaust,
let's take a minute to talk about one of the most
enduring myths in all of automotive history.
Back pressure.
The myth is that you need back pressure
to make power or more specifically low end torque
and back pressure is the resistance your exhaust fights
on its way out of your exhaust pipes.
Back pressure is actually counterproductive to making power.
You don't want any restriction in your exhaust.
Think about a Top Fuel dragster running open headers.
There's no back pressure there.
Okay, but then why do people actually lose
some of that precious low end torque
by increasing their exhaust diameter?
Well, first we have to understand that the exhaust
flowing through your pipes isn't a steady flow of exhaust.
It's pulse.
Every time a cylinder completes an exhaust stroke,
a pulse, a pulse, a pulse, pulse, pulse, pulse.
And each time one of those little baby pulses
shoots down your exhaust,
it creates a little pocket of vacuum behind it.
And just like drafting in NASCAR,
if you can get up on the guy in front of you's bumper,
you can take advantage of his little vacuum pocket.
Now we want lots of vacuum behind each of our exhaust pulses
so that the vacuum created can help pull
the next exhaust pulse out of the combustion chamber.
So this little vacuum pocket, NASCAR drafting stuff,
it's called scavenging.
And it's most effective at low RPMs
because once you get into higher RPMs,
your exhaust does start to flow,
more like a constant flow rather than the pulse.
Okay, so how do we increase the exhaust pulse velocity?
Well, think of your exhaust like a garden hose.
All right, so increasing the speed
of your exhaust gases flow.
Dang, I gotta
- [Eddie] You got a weak flow, man.
- Yeah, I know.
Well, I have, I have.
Oh God.
(laughter)
Now when the hose is wide open,
we're using all the diameter of that hose.
We've got really good flow.
There's very little back pressure
and this thing is cruising right out.
We've got a lot of flow here,
but what we don't have is very much speed.
This is coming out pretty slowly.
Now, when you decrease the diameter of the hose
without changing anything else,
you pretty clearly change the speed
that the fluid is traveling in there.
Same thing with your exhaust,
decrease the diameter and the exhaust gases
are forced to travel faster
than when the exhaust pipe is wide open.
Great flow, terrible speed.
All right, so wait a minute.
We want a small diameter exhaust to increase the velocity
to increase the vacuum behind each pulse.
So we get the scavenging effect,
but we want a big diameter, so we can have no back pressure?
Exactly.
And the problem is that obviously
you can't really have both.
So you gotta strike a compromise,
like so many things in the car world.
So this has been a really long way to say,
that you don't want back pressure, but you do want velocity
in order to get some scavenging effects
and you happen to get each of those things in opposite ways.
Okay, the end.
Let's put this on.
Before we install this,
we're gonna make sure that it's really clean
because if we have any big old hand prints
or smudges on here, and then we get hot for the first time,
that stuff will burn in to the finish.
So like if I put a thumbprint there
and we went and drove for the first time,
that thumbprint would be there pretty much forever.
So you don't want that.
Just give it a quick wipe down, before you get hot.
So, put a little,
a little lube in our hangers.
Always helps.
So, anytime we're doing an exhaust install
or something where there's multiple pieces,
you should kind of leave all the hardware
that you're working with not completely tight
so that you can get a little bit of adjustment.
So now, we've got all the parts in place
and now all we gotta do is tighten up
our exhaust fittings.
So, this hardware and that hardware there.
And then it's just time to make some noise.
Okay, so, let's take a listen
and see if this has all been worth it.
(car engine revving)
Oh, that sounds pretty good.
(car engine revving)
Not too bad.
It's not obnoxious, it's not super loud.
It compliments the intake sound.
I can still hear the intake.
(engine revving)
That sounds pretty good.
Let's take it for a drive.
(engine revving)
You know what?
That's exactly what I wanted out of an exhaust.
It's understated, it's not god-awful loud.
Oh, it's got a nice base tone to it.
(engine revving)
It makes this thing sound good.
(loud engine revving)
(soft engine revving)
Now, I don't feel any power difference.
I'll tell you that.
But, I didn't expect to.
The point of this exhaust, in our case,
isn't to give us more power now,
it's to allow us to make more power later when we add
a turbo and whatever the hell else we do to this thing.
Well, sweet.
And on that note guys,
I wanna say thank you so much for watching the show.
I hope you're learning.
We're learning a lot making it.
Make sure you subscribe to Donut
and you have the notification bell rung
so you know what's coming.
We're releasing stuff every single day.
And I appreciate you guys,
being so involved in the comments
and talking about what's going on
and telling me what you guys are working on.
Keep it up.
Let me know what you're doing,
how you're passing your time in the quarantine.
Throw in the comments, I'll be in there commenting.
I'm always in there.
And, if you guys happen to like this super sick
totally awesome shirt, you can buy it at shop.donut.com.
Join our gang with the boost creeps
and you can be one of us.
Follow me on Instagram @zachjobe
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Goodbye.